Completion percentages are bullshit 100% of the time when it comes to game development. Anyone who says "This game is X percent complete" is either delusional or a liar with the outside chance of being both. Due to how game development works it is literally impossible to sign an accurate completion percentage. Too much of what's going on development relies on other things.
Think of game development like the game kerplunk. You've got a cylinder with a bunch of sticks going through it holding up a bunch of marbles and you pull sticks out to see who winds up puling the one that lets the marbles fall, right? Right. Now imagine that instead of one game of kerplunk it's about twelve games going at the same time and they're all directly connected to each other with some sticks going through multiple games, and different types of marbles in each game with some games having a dozen different kinds of marbles all in play at once. As you pull sticks the marbles fall, but moving a stick from one means you just moved that stick in to the game next to it and that adds to the blockage of that game. Tasks constantly slow each other down, speed each other up, rely on each other to even be possible to complete, and so on and so forth. If you try to assign a completion percentage of game design you'll find it going up and down every single day because everything you do gets in the way of everything else you need to do until you finally pull enough sticks.
This is why you'll see some patreons use task lists to assign completion tallies. It's a hell of a lot easier to provide a list of the 100 things you need to do to complete and update and check them off one by one then it is to try to assign a percentage to those tasks since certain tasks will take a day, other tasks will take a week, some could take a month. Just because 50% of a list of tasks is checked off doesn't mean that 50% of the game is complete. It just doesn't work that way.
